Oxidation behaviors of wrought nickel-based superalloys in various high temperature environments

Abstract

Oxidation characteristics of Alloy 617 and Haynes 230 at 900 degrees C in simulated helium environment, hot steam environment containing H-2 as well as in air and pure helium conditions were investigated. Compared to air condition, the oxidation rate of Alloy 617 was not significantly affected in helium and hot steam environments, while Haynes 230 showed lower oxidation rate in helium environment. On the other hand, the oxide morphology and structure of Alloy 617 were strongly affected by the environments, but those of Haynes 230 were less dependent on the environments. For Haynes 230, a Cr2O3 inner layer and a protective MnCr2O4 outer layer were formed in all environments, which contributed to the better oxidation resistance. As the mechanical properties, such as creep and tensile properties, were significantly affected by the oxidation behaviors, surface treatment methods to enhance oxidation resistance of these alloys should be developed.